Diabetes mellitus and severe mental illness: mechanisms and clinical implications

The prevalence of diabetes mellitus is twofold to threefold higher in people with severe mental illness (SMI) than in the general population, with diabetes mellitus affecting similar to 12% of people receiving antipsychotics. The consequences of diabetes mellitus are more severe and frequent in people with SMI than in those without these conditions, with increased rates of microvascular and macrovascular complications, acute metabolic dysregulation and deaths related to diabetes mellitus. Multiple complex mechanisms underlie the association between diabetes mellitus and SMI; these mechanisms include genetic, environmental and disease-specific factors, and treatment-specific factors. Although antipsychotics are the mainstay of treatment in SMI, a causative link, albeit of uncertain magnitude, seems to exist between antipsychotics and diabetes mellitus. The principles of managing diabetes mellitus in people with SMI are similar to those for the general population and should follow currently established treatment algorithms. Lifestyle interventions are needed to reduce incident diabetes mellitus. In addition, improved uptake of opportunities to screen for this disease will reduce the high prevalence of undiagnosed diabetes mellitus. Currently, people with SMI receive poorer treatment for diabetes mellitus than the general population. Thus, health-care professionals in primary care, diabetes mellitus services and mental health teams have a responsibility to ensure that patients with SMI are not disadvantaged.